OLED Drain Electrode Area Control for Uniform Light Emission
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Solution Overview
Problem
Organic light emitting display devices face issues with non-uniform light emission due to thickness variations in the organic layer, particularly at the edge regions compared to the center regions, leading to degraded display quality.
Innovation Solution
The design includes a thin film transistor on a base substrate with a semiconductor layer, a gate electrode, source electrode, and drain electrode, where the drain electrode has a larger area than the first electrode, and the organic layer thickness varies correspondingly, with a surface resistance of the first electrode between 10 Ω/cm2 to 300 Ω/cm2, and the drain electrode is configured to reflect light. Additionally, the pixel defining layer has liquid-repellent properties to control the organic layer thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the organic layer is formed by printing, then the organic layer can be deposited, but the edge region becomes thicker than the center region causing non-uniform light emission
Solution Approach 1:
The pixel defining layer is designed with different opening sizes: a first opening with a smaller area and a second opening with a larger area. This creates different organic layer thickness profiles in different regions - the first region (over the first opening) has a thinner organic layer while the second region (over the second opening) has a thicker organic layer. This local variation in thickness compensates for the printing-induced thickness gradient, achieving uniform light emission across the pixel.
2Reliability
If the drain electrode has a larger area than the first electrode, then the electrical connection is improved, but the organic layer thickness becomes non-uniform at the contact region
Solution Approach 1:
The structure accepts and utilizes the non-uniform organic layer thickness created by the drain electrode's larger area. The first region (where the first electrode contacts the drain electrode) naturally forms with a thinner organic layer, while the second region has a thicker organic layer. This local thickness variation is compensated by the pixel defining layer's dual-opening design to achieve overall uniform light emission.
3Reliability
If the first electrode uses transparent conductive oxide with surface resistance of 10-300 Ω/cm2, then the electrical conductivity is optimized, but the electrode area must be precisely controlled
Solution Approach 1:
The first electrode is designed with a specific area that is smaller than the drain electrode's area. This area control is crucial for achieving the desired electrical conductivity while managing the organic layer thickness profile. The first electrode's limited area ensures that the contact region with the drain electrode creates the intended thinner first region, which is then compensated by the pixel defining layer.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration ensures uniform light emission by controlling the organic layer thickness, improving the display quality of organic light emitting display devices by ensuring consistent luminescence across pixels.
Implementation Method 1
a surface of the pixel defining layer has liquid-repellent properties
Implementation Method 2
The drain electrode may be configured to reflect light
Implementation Method 3
Holes and electrons are injected into the organic layer from the anode electrode and the cathode electrode, respectively. In the organic layer, the injected electrons and holes are recombined to generate excitons. The excitons release energy in the form of light, which is released when falling from an excited state to a ground state.
Data Source
AI summary
Embodiments of the present invention include an organic light emitting display device and a method for fabricating the same. The organic light emitting display device may include a thin film transistor on a base substrate and including a semiconductor layer, a gate electrode, a source electrode, and a drain electrode; and an organic light emitting diode, which includes a first electrode connected to the drain electrode, an organic layer on the first electrode, and a second electrode on the organic layer. The drain electrode may have a larger area than the first electrode.